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Triggering an IR receiver from a white object/paint

 
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Sat May 30, 2009 4:08 pm    Post subject: Triggering an IR receiver from a white object/paint Reply with quote

I have started to build a system/circuit to capture old cine 8/super 8 using the Cinecap programme.

I am having trouble to get the IR receiver being triggered when a white blade moves passed the IR receiver.

(There are three blades of which I have painted one white i.e. 2 black blades will pass before the white blade is supposedly required to trigger the system)

For the system I used the following-
A cine projector that can run as slow as 3 frames per second (Eumig 610D).

The moment that the frame "stops" for a split second, you need your camcorder to record the image and these frames are put together by the Cinecap into an AVI file. So when the frame stops, a trigger needs to be activated. In this case an IR receiver is the trigger.
(I also tried with a microswitch, but the capturing was erratic)

My video camera is a 3CCD Panasonic NV GS250

I have done the following: I converted a mouse (acknowledge James Rueben):



Used the following circuit (acknowledge James Rueben)::



Connected to an IR receiver:
OPB608A


http://www.datasheetcatalog.org/datasheets2/22/229105_1.pdf

The IR receiver and all my connections (converted mouse; circuit board) are working well.

My finger, or any white paper triggers a signal which captures a frame via my camcorder on Cinecap, BUT, the paper, my finger, etc need to be very close to the surface of the IR receiver to trigger the signal.

As mentioned before, I painted one of the three blades white, which will hopefully be triggered by the white blade going past.(acknowledge James Rueben):




It only works when I bring the IR receiver very close to the stationary blade.

If the blade rotates at 3fps, it does not trigger a signal, although I bring the receiver quite close.


What is the solution?:

I can see two possibilities
1. Either put something on the blade ? white paper, other material which the IR receiver will pick up (this is where I need advice and this will be the easiest),
2. Or get a stronger?? IR receiver.

I feel that there must be a way to produce a strong input by means of some material to create the trigger. I used PVA paint.

Any advice will be helpful. Will try it out in the next week or two.

Regards
Albie

I need to acknowledge the help I got from James Rueben in this regard- he initiated the project, with the initial input fro Ronypony.
Having Trouble with DIY Telecine (8mm) System - VideoHelp.com
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Sun May 31, 2009 4:30 am    Post subject: Reply with quote

Just more detail I want to add:

The distance is very close ± 1-2mm, before the switch is triggered. So if I wave a white piece of paper 1cm in front of the detector, it does not trigger it.

This is how the set-up should be:

Projector projects to a lens (the Eumig allows for speed to go down with a gear system to 3 fps), produce an ariel image which is captured at 3fps. This is not my set up.




Initially tried a microswitch, but this works erratic, especially at the start of film





Cinecap program- screenshot





The photo that I have posted of the IR receiver next to the blade, is not mine. I havent fixed mine, but this is how I painted a blade.

Someone advises that in stead of paint, I use a thin mirror or foil on the blade. Any comments on that?
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Tue Jun 02, 2009 4:07 pm    Post subject: Reply with quote

Sorry for the delay in response. I was a quite busy and am just having a bit of time to look through the data sheet you provided.

That sensor needs to be very close to what it is reading. The diagram in the data sheet shows the measured item .11 inches away from the internal sensor. There is also .05 inches of material between the internal sensor and the outside of the case so that means that the measured item needs to be .05 inches from the front of the sensor housing (1.27mm). So it sounds like your experimental results are correct.

Based on the 1.7 volt forward voltage on the LED you are driving it at around 18.3mA which is close to the 20mA that the data sheet tests were performed at but you may get a bit better results if you increase the current a bit, there is a 50mA max so there is lots of room to play. If you want I would aim for around 30mA.

I have always been a fan of the sensors that have a tab that goes into them and breaks a beam. The concept is the same as your sensor but instead of looking for reflected light it looks for the beam being broken by something opaque. This may make it a bit more reliable but I am not familiar with the setup so there may be something that prevents this from being used.

http://www.fairchildsemi.com/ds/MO/MOC70P3.pdf
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Wed Jun 03, 2009 2:24 pm    Post subject: Reply with quote

Thanks for the reply. I have had some other responses from other websites, so you might want to comment.

With regards to pick up, I have had advice as follows;

-Use an IR light or LED light and mount it so that it shines on the white blade
-Either paint the blade aluminum, or use a thin mirror on the blade.


Some felt I should change the R2 value to much higher e.g. 100k resistor and reduce R1 to 68 to 72 ohm.

Any comments so far?

If that doesn't work, I might get a photo interrupter as you mentioned. But as all three blades will be going through the slit, I will need to "extend" the one blade so that only one out of three goes through the slit and triggers the switch. What material would you suggest? I really like the photo interrupter possibility. Please look at the following site and advise. The dealer is close to me

http://za.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&binCount=47&Ne=4294958012&N=4294781996+4294955625

Regards
Albie
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Wed Jun 03, 2009 2:47 pm    Post subject: Reply with quote

Since you already have it designed and built I would first try mounting the sensor about 1mm away from the area to be detected and see if it works. That is the distance it was designed for. I am thinking that the LED and transistor optics are probably angled so that it will reflect best against a surface that is at the specified distance so with this device I don't think you will ever get good range.

Changing those values may help but I think it should work fine as is.
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Tue Jun 16, 2009 5:56 am    Post subject: Reply with quote

I need serious help. This is my set-up so far:




On request, I tested values at different points, using the original configuration (R1 180 Ohm; R2 6k8 Ohm)

Here are the results:

With the IR detector facing away from the blade:

A: 1.3V
B: 3.4 V
C: 3.4 V
D: 4.25 V

With the IR detector facing towards the stationary blade:

A: 1.3V
B: 1.55 mV
C: 3.4 V
D: 4.25 V

Quote:
Projector off, blades stationary and turned away from the IR receiver: measure the 5 V (point E), 3.3 V (point F) and signal (point G)
.


E: 4.25
F: 3.4
G: 3.4

Quote:
Projector off, blades stationary and white painted blade in front of the IR receiver: measure the 5 V (point E), 3.3 V (point F) and signal (point G).



E: 4.25V
F: 3.4V
G: 155mV

Quote:
As a final check on the cables, measure between the zero volt point on the detector circuit and the zero volt point on the mouse. The projector state doesn't matter for this one. This should of course be zero or very close to it.


0.02mV

So it looks as my point E just produces 4.25V.

With R2 replaced by 100k Ohm

B (Output) Stationary: 3.1V (facing away from white blade)
Facing white blade: 0.07 mV
Moving: 2.4Volt
Does not trigger “Capture” on Cinecap

With R2 replaced by 100kOhm and R1 replaced by 68 Ohm:

B: Stationary: 3.38V (facing away from white blade)
Facing white blade: 0.37 mV
Moving: 1.68Volt
Does not trigger “Capture” on Cinecap

So, I am not sure what I am doing wrong.

I bought this Slotted IR optical switch yesterday (OPB365T), just in case I get stuck: Datasheet:
http://www.digchip.com/datasheets/parts/datasheet/344/OPB365P55.php



Does the beam need to be broken in that first 1mm transparent part, or does the object need to go deeper in the slit?



If so, I can try to mount it close to two movable parts, that move only when a frame advances (so it is stationary and then either move down- that white piece)


Or to the right:


These two possible trigger points are very consistent.

So, should I try this optical switch, I need to know the following
1. How deep should the object need to go in the slit (because if it needs to go deeper, it might be difficult)II thought of attaching a rigid plastic to the "moving" side of one ot the trigger points.
2. What wires should be connected to what pins (For me this is very important, being a newbie to electronics)
3. Do I need resistors?

Thanks
Albie
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Sat Jun 20, 2009 2:14 pm    Post subject: Reply with quote

I have used my IR detector and mounted it to the rear trigger.

R1: 68 OHM
R2: 100k

Picture of the triggering system- works wel, up to now:



The silver paper moves up and down and trigger the IR detector

Any advice?
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Sun Jun 21, 2009 2:38 am    Post subject: Reply with quote

I would say if it works stick with it. Congrats on figuring it out.
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avz10
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Joined: 30 May 2009
Posts: 6

PostPosted: Tue Jun 30, 2009 11:32 am    Post subject: Reply with quote

I'm still struggling, because the switch get triggered erratically at some times. So I thought of trying the OPB365T. I quote this from another site:


Quote:
Originally Posted by 2xCPU View Post
Use the same circuit as you've used for the OBP608, but alter the pinout as below.


Pin equivalents
OPB365T........OPB608A......(Function)
....1................3................Anode
....2................4................Cathode
....3................1................Collector
....4................2................Emitter







I am not really sure what wire should go to what pin. Is it possible to number them for me next to the sensor? (Does it start right top with nr 1 and then clockwise to nr 4 next to 1?) Remember James changed the numbering on the diagram

Thanks
Albie
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